Voice refers to whether the subject of a sentence performs an action (active voice) or receives an action (passive voice). In the active voice, the subject performs the action and the object receives it. In the passive voice, the object becomes the subject and the subject is either not mentioned or follows the verb in a prepositional phrase using "by". The passive voice forms require a linking verb like "be" and the past participle form of the main verb. Passive voice transformations can occur for all verb tenses and with modal verbs. Examples are provided to demonstrate active and passive voice sentences.